Piping networks formed by joining pipe segments using mechanical couplings require that the ends of the pipe segments be prepared to be received by the mechanical couplings. Mechanical couplings do not use solder, brazing or welding to effect a pipe joint. One type of mechanical coupling uses resilient, angularly oriented radial teeth located within a coupling housing to capture and retain the pipe segment within the housing. The end of the pipe segment is inserted axially into the housing where the teeth engage a groove formed in the outer surface of the pipe end. A fluid tight joint is effected by an elastomeric seal, such as an O-ring positioned within the housing and engaging both the housing and the pipe segment.
Another type of mechanical coupling uses arcuate clamping segments which are bolted to one another and fit circumferentially around adjacent pipe ends to hold them together. The clamping segments have circumferential keys that face radially inwardly toward the pipe ends and engage circumferential grooves formed in the outer surfaces of the pipe ends. A sealing element is located in an interior space between the clamping segments and the outer surface of the pipe end to effect a fluid tight seal.
To join pipe ends using mechanical couplings, pipe stock is cut to length and the end is then prepared for engaging the mechanical coupling by radiusing or chamfering the end of the pipe, forming a groove in the outer surface of the pipe in spaced relation to the radiusing/chamfered end, and forming a depth indicator mark on the pipe also in spaced relation to the pipe end. The radiusing/chamfered end acts as a lead in to permit the pipe to be more easily inserted into the coupling housing, retainer and elastomeric seal, the radiusing/chamfering process removing burrs or sharp edges which could damage the elastomeric seal. A radiused or chamfered end also allows the use of seal designs having more interference and/or greater radial compression which facilitates effective sealing over a wider range of pipe surface conditions, tolerances and ovality or out of roundness. The groove provides a bearing surface which the resilient teeth of the coupling can engage to hold the pipe end fast to the coupling against pressure loads, as well as other mechanical separation loads which may otherwise cause the pipe segment to separate from the coupling. The groove must be positioned at the proper distance from the chamfered end compatible with the coupling so that the elastomeric seal engages the pipe end when the teeth engage the groove in the pipe. The depth indicator mark is positioned at a distance from the pipe end so that, when the mark is aligned with a reference index on the coupling, it provides a visible indication that the groove has been engaged by the teeth and the pipe end is properly seated against an internal stop within the pipe coupling housing. Both of these internal features are not visible to the pipe installer, and hence the advantage provided by the depth indicator mark.
Pipe preparation devices use support rollers mounted on a rigid body to circumferentially engage and support the pipe end, with special tool rollers which radius or chamfer the pipe end and form the groove and depth indicator mark when the device is rotated relatively to the pipe end. For smaller pipe diameters, this process can be effected manually in much the same way as small diameter pipe segments are cut using a pipe cutter. However, merely adapting a pipe cutter to radius or chamfer and groove pipe ends has various disadvantages. The same tool roller cannot be used to prepare pipes of differing diameters because the spacing between the radius/chamfer, the groove and the depth indicator mark is different for each different diameter. Thus, separate tools or interchangeable tool rollers are required depending upon the diameter of the pipe being prepared. Furthermore, the force required between the tool roller and the pipe to form the radius/chamfer, groove and depth indicator mark may cause the pipe end to distort unacceptably into an out of round shape, rendering the pipe end useless because, being excessively out of round, it will not be insertable into the coupling. Pipe end distortion will occur most often when the support rollers and the tooling rollers are not properly spaced at substantially equal angles circumferentially about the pipe end. Rollers on typical pipe cutters do not support the pipe end at equal spacings and the geometry of the rollers is not variable to accommodate pipe segments having different diameters.
There is clearly a need for a pipe preparation tool which is adaptable to different pipe diameters and which will have less potential for distorting the pipe end out of round.